I'm taking on a Battleborn replacement of lead acid batteries in my new-to-me 2013 AI Ext Lounge, and from what I've learned from users like gmillerok1 and lewster, uncle_bob, and others in the forums here is that you'd remove the OEM BIM and add a dc-dc charger between the alternator and the batteries. There are several threads where this is discussed as a peripheral part of the main conversation, but I haven't found a detailed thread on this topic specifically. Here's an example of one
http://www.airforums.com/forums/f240...ml#post2222648
My components will be delivered in the next week or so and I'll be tackling this project shortly thereafter to get ready for our first trip out on the rig around Lake Michigan.
Hopefully some users with experience in this can weigh in with their recommendations as I've had to piece things together from several threads.